"Just as knowledge of language cannot be separated from our more general knowledge of the world, so Davidson argues that knowledge of oneself, knowledge of other persons and knowledge of a common, 'objective' world form an interdependent set of concepts no one of which is possible in the absence of the others."
--Jeff Malpas, Stanford Encyclopedia of Philosophy

To figure out which of the many conceivable versions of that position Davidson actually holds, I'll have to go hunting for a copy of the essay "Three Varieties of Knowledge". I'll report when I figure something out, as if anyone else actually cared.